The disclosure relates generally to magnetic resonance elastography (MRE) and, more specifically, to a phantom for MRE quality assurance.
MRE is gaining wider clinical applicability due to its ability to noninvasively and quantitatively measure tissue stiffness. MRE is a multi-step process beginning with the induction of shear waves into the tissue to be examined via an external source of vibration. The shear waves are then imaged with a phase-contrast MRI pulse sequence with motion-encoding gradients synchronized with the applied vibration. The resulting wave images of the wave motion are inverted to produce an elastogram image and calculate a mechanical property of the tissue.
MRE is analogous to manual palpation, which has a long history in the practice of medicine as a clinical diagnostic tool for examining tissues such as the breast and thyroid for focal and diffuse diseases. In fact, MRE of the liver has already matured to a point where it is replacing needle biopsies for the diagnosis of fibrosis and cirrhosis in a growing number of clinical practices.
To assure accurate calculations of the mechanical properties, routine calibrations are required. As generally described above, MRE utilizes the oscillating stress produced by the shear waves that propagate through the organ, or tissues to be imaged, to elicit information about the tissue. Thus, to perform calibrations, specialized phantoms have been created that are formed of particular materials that are both MR-visible and have known stiffness/elasticity. Unfortunately, the properties, including the stiffness/elasticity of these materials change over time and can vary due to fine differences in the manufacturing process. Thus, these specialized MR-visible elastography phantoms must be regularly replaced and it is challenging to ensure that phantoms used for calibration at different sites have matched properties.
Thus, it would be desirable to have calibration and quality control systems and methods for MRE that do not rely on the variable properties of a specialized material.